Bit.



E. T. McPHERSON.

I BIT. APELICATION FILED MAY l0. I918.

Patented Apr 8, 1919.

T. MOPHERSON, OF WILMINGTON, OHIO, ASSIGNOR TO THE IRWIN AUGER BITCOMPANY, OF WILMINGTON, OHIO, A CORPORATION OF OHIO.

BIT.

Specification of Letters Patent.

' Patented Apr.'8,1919.

Application filed May 10, 1918. Serial No. 233,616.

To all whom it may concern:

Be it known that I, ELMER T. MCPHERSON,

, a citizen of the United States, residing at Willowingisaspecification, reference being had 7 therein to the accompanyingdrawing:

This invention relates to bits for boring holes in wood, and it isapplicable to auger bits, brace bits, machine bits and the like. Itcomprises an improved construction which is less liable to clog withchips than the forms now in use. In particular the invention comprises adouble cutter bit having a single twist shank, and a portion of thetwist being cut away opposite one of the cutting edges. Thus a greatlyincreased space is left for the passage of the chips.

In the drawings, Figures 1 and 2 are views of such a bit havlng spu-rsand extension lips, and especially adapted to fairly soft wood, theseviews both being elevations but at different angles; Fig. 3 is a viewsimilar to Fig. 1, but showing a bit having a flat head and no spurs andbeing particularly adapted to use in hard wood; and Fig. 4 shows the oldform of bit merely for comparison; Figs. 5 and 6 are end views of Figs.1 and 4 respectively.

The drawings show bits of the solid center type having the usual shank 1and solid center or stem a surrounding which is the twist 2 integralwith the stem. .In the form of Figs. 1 and 2 the twist ends in a cutter3 including a spur 4 and an extension lip 5 having a cutting edge 6.Also the stem a has integral therewith a second partial twist 7 near thecutting end of the bit, this second twist being provided with a spur 8and an extension ip 9 ending in a cuttin edge 10. The twist 7 is notcomplete as is t e twist 2, it being cut away at the portion 11 immedi:ately at the rear of the spur 8. The different construction thusproduced will be evident from comparing Figs. 1 and 2 with the olderform of Fig. 4. In Fig. 4 the parts are similarly numbered, but eachnumeral of Fig. 4 is given the suffix a and it will be seen in Fig. 4that the portion 11 of the partial twist is carried around to a pointadjacent the cutting edge 6. In Figs. 1 and 2 on the contrary the twist7 terminates in a plane from the rear of the spur 8 to the stem 1.

Thus a much larger space is left between the partial twist 7 and thecutting edge 6 than in the form of Fig. 4 and thereby chips pass outmore easily and do not clog the. bit.

The form of Fig. 3 will be clear from.the previous description, the bitof this figure being adapted to hard wood. It has no spurs, but isprovided with a cutting edge 12 and a side lip 13 on the partial twist14. Here also the partial twist is cut away in a plane passing from therear end of the side lip 13 directly to the stem of the bit. Theadvantages of the form of Figs. 1 and 2 are found also in the form ofFig. 3. In both the new forms the partial twist terminates directly atthe rear of the cutter in a plane reaching directly to the solid centerof the bit.

In the ordinary bit, such as is shown in Fig. 4, the angle between thecutting edge 1% and the plane 11 at the rear of t e cutter isapproximately 160 measured around the stem, while in the new forms ofFigs. 1 to 3, the corresponding angle is about 80 or somewhat less thana right angle. Also, the pitch of the twist 2 is greater in the newforms than the pitch of the partial twist 7 but the pitches of thetwists in Fig. 4 are the same. Thus in the forms of Figs. 1 to 3 thetwists gradually separate as the plane portion 11 is approached.

These two changes in the construction provide the additional space forthe chips to obvious modifications will occur to a person skilled in theart.

Having thus fully described my invention, what I claim as new and desireto secure by letters patent, is

1. In a bit, a solid center having an integral twist ending in a cuttinedge and an integral partial twist also en ing in a cutting edge, thepartial twist being cut away on a plane substantially at right angles tothe axial plane in which the main cutting edge lies and intersectingsaid cutting edge at its juncture with its solid center.

2. In a bit, a solid'center having an integral twist ending in a cuttinedge, and an integral partial twist also en ing in a. cutting edge, thepartial twist being cut away adjacent the cutting edge of the completetwist in a plane substantially at right angles therewith and reachingfrom the rear of said partial twist to the center of the bit.

3. In a bit, a solid center having an integral twist thereon, said twistending in an extension lip having a cutting edge and also having aprojecting spur, a partial twist on said center near the cutting end ofthe bit, said partial twist having a similar extension lip ending in acutting edge and a projecting spur, the partial twist being cut awaydirectly at the rear of its spur in a plane reaching from said spur tothe sol1dcenter and substantially at right angles to the cutting edge ofthe complete twist.

4. In a bit, a solid center having an in-, tegral twist thereon endinina cuttmg edge and an integral or partia twist also ending in a cuttingedge, the partial twist being cut away to provide an angular open spaceof portion of the complete tw st.

In testimony whereof, I aflix my signature.

ELMER T. MGPHERSON.

